"The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."
I forget where I read that. Some fiction author, maybe...
Note that they actually caught some when they abandoned their checkpoint and went about doing what they're supposed to do.